Motor-control system



C. T. HENDERSON.

MOTOR CONTROL SYSTEM.

APPLICATION FILED SEPT. 14, I908.

Patented 001. 31, 1922.

Patented Oct. 31, 1922.

UNITED STATES PATENT OFFlCE.

CLARK EN N, OF MILWAUKEE. WISCONSIN. ASSIGNOR TO THE CUTLER- HAMMER MPG.00., OF MILWAUKEE, WISCONSIN, A CORPORATION OF WIS- CONSIN.

MOTOR-CONTROL SYSTEM.

Application filed September 14, 1908.

J '0 all whom it may concern Be it known that I, CLARK T. HENDERSON, acitizen of the United States, residing at Milwaukee, in the county ofMilwaukee and State of \Visconsin. have .invented new and usefulImprovements in MotonControl Systems, of which the following is a full,clear, concise, and exact description, referencebeing had to theaccompanying drawing, forming a part of this specltication.

This invention relates to a motor control system. I

Among the objects of the invention is to provide a motor control systemhaving a controller in which amaximum number of control positions issecured with a minimum number of switches.

Other objects and advantages will. hereinafter appear.

The invention as applied to a compound motor, is illustrated in theaccompanying drawing.

For the salve of clearness, the several appliances employed in the motorcontrol sys tem have been illustrated in elementary forms, and variousauxiliary parts that in practice may be associated therewith have been.discarded.

The compound motor is provided with an armature A. a series field F anda shuntiield S, Of course, the motor may be of any suitable type. Thecurrent for operating the motor is supplied from conductors 1 and 2which are connected respectively to the positive and negative supplylines. Qne terminal of the motor may be connected to the positive supplyline through the resistances R R and Between the other side of the motorand the negative supply main is arranged a switch 3, which is actuatedby a solenoid 4. Switches 5, 6 and 7, which are actuated by solenoids 8,9 and 10, are connected with the resistances and when said switches areclosed said resistances are short-circuited.

\Vhen the switch 3 is closed, the motor is connected between the supplylines. If the switches 5. 6 and T be open, the resistances It, R and R.will be in series with the armature. Of course, the resistances may beconnected in circuit in any suit-able way to perform the desiredfunction. These resistances may be sbort-circuited by closure Serial No.452,884.

of the switches 5, 6 and 7, as will be hereinafter explained.

For the purpose of establishing a dynamic braking circuit around themotor, a switch 11 actuated by a solenoid 12 is provided.

In order that the motor may be run in a reverse direction, a switch 13operated by a solenoid 14 is provided. This switch serves to connect apoint between the armature and series field to the ne ative line throughan auxiliary resistance 3 7 The operation of the various switches isdirected by means of a master controller M. It will be assumed that themaster controller is of the drum'type and that its handle may be turnedto either the right or the left from the off position. In thedrawingthere is shown a simple development of the master controllerwhich will be readily understood by those skilled in the art. Thecontroller drum provided with a segment a on which bears a fingerconnected to the positive line. On the left-hand side of the drum arearranged segments 7), 0, (Z, c and f and on the right-hand side.segments I), g, h, (2, e and 7'. Suitable contact fingers are arrangedto engage the segments and pass over them as the drum is turned Thesefingers are represented in the drawing by circles arranged in a verticalline down the center of the development. From these fingers, connectonsextend to various parts of the controller. Vhen the handle is in the offposition, the segments h, (z, (7 c and f" are engaged. by theirrespectivefingers.

As previously stated, the controller handle may be turned either to theleft or to the right. Connect-ions are provided whereby the motor willbe run in the forward direction if the handle be turned in one of thesedirections and will be reversed it the handle be turned in the otherdirection. In either direction there are four different positions towhich the drum may be turned, and these positions are indicated bydotted lines upon the development.

In describing the operation of the controller, it will be assumed thatit is used to control a motor which is employed to operate a hoistingand lowering mechanism. The brake of this mechanism may be released bymeans of a solenoid B in any suitable manner known in the art.

If it be desired to hoist the load, the motor is run in a forwarddirection. Accordingly, the controller handle is turned to bring theleft-hand segments into engagement with the contact fingers. When thedrum reaches the first position, the segments Z) and 0 will be engagedby their respective lingers. Accordingly the brake solenoid will releasethe brake and the switch 3 will be closed. As previously stated, thefinger bearing on the segment a is connected to the positive line. Hencecurrent flows from the positive line through conductor 1, conductor tothe segment a and thence to the other segments through suitableconnections. The circuit of the brake solenoid B extends from thesegment 6, through conductor 16, brake solenoid B, conductor 17 andconductor 18 to the negative line. The circuit of the solenoid. 1extends from the segment 0 through conductor 19, solenoid at to thenegative line.

The motor will now ruri in the forward direction and hoist the load. Themotor cur-- rent flows from the positive line through conductor 1,resistances R R and R se ries field 1*, armature A, switch 3 andconductor 2 to the negative line. The shuntfield S is connected directlyacross the con ductors 1 and 2 and thus energized, save when the lineswitch L is open.

As the drum passes through the second, third and fourth positions, thesegments d, c and f are engaged successively by their re spectivefingers which are connected respec tively to the solenoids 8, 9 and 10.Hence, switches 5, 6 and 7 will be closed successively, therebyshort-circuiting resistances R R and Inasmuch as these switches are thusclosed one after the other, the resistance is removed from the motorcircuit gradual- 1y as the speed of the motor builds up. The drum may beplaced in any one of these positions to include more or less resistancein the motor circuit for the purpose of giving the motor differentspeeds. One terminal. of each of the solenoids 8, 5) and 10 is connectedto the conductor 18. said solenoids are connected to the fingers ofsegments d, e and f, respectively, by means of conductors 19, 20 and 21.The circuits of these solenoids extend from the drum through conductors19, 20 and 21 and solenoids 8, 9 and 10 in parallel and thence throughconductor 18 to the negative line.

lVhile the drum is in the off position, the solenoids 8, 9 and 10, areall energized as segments cl, e and 7 are engaged by their respectivefingers. Hence switches 5, 6 and 7 are closedand the resistances R R andR are thus short-circuted. The switch 11 is also closed. as its solenoid12 is connected in circuit by means of the segment 71 which is engagedby its respective contact finger. The

The other terminals of 1 sa-ps5 ductor 25, conductor 1, switches 5, 6and 7,

and series field F to the other side of the armature.

If it is desired to lower the load, the master controller is moved tobring the righthand segments into engagement with their contact lingers.in the first position, the segment 7)? will engage .its respectivefinger and close the circuit through the brake solenoid. The circuit ofthe brake solenoid can be traced from the segment 7) through the samepath as was previously described. The resistances are nowshort-circuited and the armature A, series field F and resistances R Rand R are connected in a closed circuit by means of the switch 11. Thisclosed circuit foru'is a dynamic braking circuit. if the load be heavy,it will descend of its own weight, thereby driving the motor armature.In consequence, the motor armature will develop a braking current whichwill flow through the braking circuit and cause the motor to retard thedescent of the load. Under certain conditions of operation, the brakingaction will be so great that the load. will descend very slowly. If theload is not heavy, it is quite probable that it will he unable toovercome the inertia and friction of the mechanism, and hence it willnot start to descend of its own weight. In such a case it is necessaryto reverse the motor by current taken form the line. To do this, thecontroller is moved to the fourth position on the right. As it passesthe first, second and third positions, the segments f, c and (Zdisengage their respective fingers; and hence switches 7, 6 and 5 areopened, therehv inserting resistances fi and R in the braking circuit.When the controller reaches the fourth position, switch 13 is closed,the circuit of its solenoid being closed by segment g engaging itsrespective finger. The circuit of this solenoid may be traced fromsegment 9, through conductor 26, solenoid. 141 and conductor 27 to thenegative line. Switch then establishes a circuit which leads from thepositive line, through conduc tor 1 and then divides. One division ofthe circuit extends through conductor switch 11, conductor 24 andarmature A and the other through resistances R R and and series field F.The divisions of the circuit then reunite at a point between ari'nature.1 and series field F and from there the circuit extends throughauxiliary resistance R, conductor 28, switch 13, conductor 27 andconductor to the negative line. The a uxiliary resistance R protects themotor armature from an excessive current. lt usually only necessary toleave the controller in the fourth position but an instant, as it ismerely necessary to give the load a start and then it will descend ofits own weight. The master controller is then moved back through thethird, second and first positions. By moving it in this manner, theresistances R R and R are short-circuited successive ly, therebyincreasing the dynamic braking action of the motor, as the less theresistance the lower the speed at which the armature will rotate under agiven load. lVhen the load approaches the position where it is stopped,the master controller may be moved. to the off position, thereby causingthe full dynamic braking action of the motor and applying the mechanicalbrake.

By connecting the motor to one side of the line, at a point intermediateof the armature A and the series field F, the armature A and the seriesfield F being connected in parallel to the other side of the line, I amenabled to reverse the motor and keep the series field in circuitwithout the necessity of providing any additional switches for thepurpose of reversing the connections of the series field. Theshunt-field S is connected directly across the line, and hence itspolarity is constant. The series field F is so connected in circuit thatthe current always flows through it in the same direction. irrespectiveof the connections that are established by the several switches. heneither the switch 3 or 13' is closed, current flows through the seriesfrom right to left and when these switches are open and switch 11 isclosed the braking current always flows through it in the samedirection. Hence. its polarity is always the same. The flow or? currentis merely reversed in the armature circuit. When switch 3 is closed, thearma ture current flows from right to left. \Vhen switches 13 and 11 areclosed, the armature current flows from left to right and when simplyswitch ll is closed, the braking current flows from right to left. Theauxiliary resistance R" protects the armature against an excessivecurrent when switch 13 is closed to reverse the motor.

The number of switches that are required. in the controller to run themotor in either the forward or reverse direction and to cause the motorto act as a dynamic brake and to enable the series field to be arrangedin the braking circuit, is less than has been re quired in otherstructures. To obtain all these results, at least one or more switcheshave been required in addition to those which are employed in thecontroller herein described.

The invention set forth herein is, of course, susceptible of otherembodiments and adaptations.

The invention claimed is l. A. motor control system comprising a motorhaving a. series field, a switch 'lor connecting one terminal. of thearmature to the source of electrical. energy, another switch forconnecting the other terminal of the armature to the source ofelectrical energy at a point between the armature and the series field,and a third switch tor connecting a dynamic braking circuit across themotor armature whereby said series field is connected in said brakingcircuit.

A. motor control system comprising a motor having a series field, aswitch for connecting one terminal of the motor armature to the sourceof electrical energy, another switch for connecting a point between saidarmature and said series field to said source of electrical energythrough a resistance, and a third switch for connecting a dynamicbraking circuit across the motor armature in a manner to include theseries field in said braking circuit.

3. In a motor control system, a motor having a series field. aresistance arranged to be connected in circuit with the armature andseries field. of said motor, an electromagnetically operated switch forconnecting one terminal of the motor armature to one side of the sourceof electrical energy, and two other electromagnetically operatedswitches. one to connect a point between said armature and said seriesfield to one side or the source of electrical ener; and the other toclose a dynamic braking circuit including said armature, said seriesfield and said resistance.

4. In a motor control system. a motor having a series field, aresistance arranged to be connected in circuit with the armature andseries field of said motor, an electromagnetically operated switch forconnecting one terminal of the motor armature to one side of the sourceof electrical energy. and two other electromagnetically operatedswitches, one to connect a point between said armature and said seriesfield. to one side of the source of electrical energy and the other toclose a dynamic braking circuit including said armature, said seriesfield and said resistance, and a master controller for directing theoperation of said switches.

In a motor control system, a motor having a. series field, resistanceadapted to be connected in circuit in series with the. motor armatureand the series field, electromagnett cally operated switch forcontrolling said resistance, a switch for connecting one ter minal. ofthe motor armature to one side of the source of electrical energy,another electromagnetically operated switch for connecting a pointbetween the motor armature and the series field to one side of thesource of electrical energy through a resistance, and a thirdelectromagnetically operated switch for connecting a dynamic brakingcircuit to include the armature, the series field and the firstmentioned resistance.

6. In a motor control system, a motor having a series field, aresistance adapted to be connected in circuit in series with the motorarmature and the series field, electromagne cally operated switch forcontrolling said resistance, a switch for connecting one terminal of themotor armature to one side of the source of electrical energy, anotherelectromagnetically operated switch for connecting a point between themotor armature and CLARK T. HitNDERSON.

lVit-nesses S. W. FITZG RALD, R. S. ULRIon.

